In recent years, for use in such equipment as street lamps, surveillance cameras, and unmanned communications stations that are used in a situation that battery replacement cannot be done frequently, power supply systems which supply power to a load through cooperation between a main power source such as a backup built-in battery and an auxiliary power source such as a fuel cell or a solar cell have come to attract attention.
Such power supply systems are equipped with, as an auxiliary power source, a power source for supplying power to a load while suppressing the consumption of power supplied from a main power source. In many of such power supply systems, the auxiliary power source not only supplies power to the load but also stores excess power in a power storage unit (e.g., a lithium ion battery).
Electronic apparatus are known which are equipped with, as a power source unit, a main power source and an electric generator for an auxiliary power source and requires almost no battery replacement (refer to Patent Literature 1, for example).